Typhoon Ketsana, known in the Philippines as Tropical Storm Ondoy, was the second most devastating tropical cyclone in the 2009 Pacific typhoon season with a damage of $1.09 billion and 747 fatalities, only behind Morakot earlier in the season, which caused 789 deaths and damages worth $6.2 billion. The storm was the sixteenth tropical storm, eighth typhoon and the second major typhoon in the season. It was the most devastating typhoon to hit Manila,[1] surpassing Typhoon Patsy (Yoling) in 1970.

Ketsana formed early about 860 km (535 mi) to the northwest of Palau on September 23, 2009. The depression remained weak and was downgraded to a low pressure area later that day by the Japan Meteorological Agency and after drifting through extremely favorable conditions, it intensified the next day and was categorized as Tropical Depression by the Philippine Atmospheric, Geophysical and Astronomical Services Administration and was given the name Ondoy after entering the Philippine Area of Responsibility. The Joint Typhoon Warning Center issued a Tropical Cyclone Formation Alert on the depression. It was then upgraded to a tropical depression by the JMA later that morning before the JTWC followed suit early on September 25, designating the depression as 17W. Soon, Ketsana was upgraded to a Tropical Storm before passing over the Philippines. As it moved into the South China Sea the storm intensified while moving toward the west, and was categorized as a Severe Tropical Storm by the JMA.

Philippine President Gloria Arroyo declared a "state of calamity" encompassing most of Luzon after at least 86 people were initially reported dead in landslides and other incidents.[2] Flood water levels reached a record 20 feet (6.1 m) in rural areas. As of October 24, 2009, at least 464 deaths in the Philippines were officially reported from the typhoon.[3][4][5][6][7][8][9]

On September 23, 2009, the Japan Meteorological Agency (JMA), reported that a seasonal tropical depression had formed about 860 km (535 mi) to the northwest of Palau.[10] The Joint Typhoon Warning Center (JTWC) then reported later that day that the depression had a developing low-level circulation center and was in a favorable environment with low vertical wind shear.[11] The JMA then reported that the depression had weakened into an area of low pressure.[12] However, early the next day, as deep convection started to consolidate around the low-level circulation center, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) reported that the low pressure area had become a Tropical Depression and assigned it a local name of Ondoy.[13][14] Later that morning, the JTWC issued a Tropical Cyclone Formation Alert as central convection had continued to organize around a consolidating elongated but exposed low-level circulation center.[15] The JMA then re-upgraded Ondoy to a tropical depression later that morning before the JTWC followed suit early on September 25, designating it as Tropical Depression 17W when it was located about 400 nm east of Manila in the Philippines.[16][17] At this stage, the system was moving along the southern side of the subtropical ridge and had good poleward outflow into a tropical upper tropospheric trough (TUTT) cell.[17]

Tropical Storm Ketsana over the Philippines on September 26

Throughout September 25 the intensification of Ondoy was hampered by the system moving into an area of moderate vertical wind shear and by an upper-level trough of pressure that was moving over the system.[18] But later that day the JTWC upgraded it to a Tropical Storm despite its low level circulation center being partially exposed.[19] The JMA followed suit early the next day, assigning the international name of Ketsana and the international designation of 0916 to the storm.[20] PAGASA then reported that Ketsana had made landfall on Northern Luzon near the boundary of the Philippine provinces of Aurora and Quezon. As a result of making landfall, its low-level circulation center had become fully exposed, but as the storm moved into the South China Sea, it dramatically deepened and expanded while moving west and was upgraded to a Severe Tropical Storm by the JMA early on September 27.

During September 27, Ketsana gradually developed further and was upgraded to a Typhoon by the JTWC and the JMA early the next day, as multiple convective bands were continuing to consolidate more tightly around the low-level circulation center, leading to the formation of a disorganized eye. Typhoon Ketsena then intensified quickly under favorable conditions, reaching peak windspeeds later that day of 165 km/h, (105 mph) (1-min winds) and 140 km/h (85 mph) (10-min winds) which made it a Category 2 typhoon on the Saffir–Simpson hurricane scale. Ketsana then made a second landfall on Quảng Nam in Vietnam, at 0600 UTC on September 29 at its peak intensity. It then rapidly weakened into a Severe Tropical Storm, with the JTWC issuing its last advisory later that day; however, the JMA continued to monitor Ketsana as a Severe Tropical Storm until later that day, when it downgraded it to a Tropical Storm before further downgrading it to a Tropical Depression early the next day when the center of the depression was located over Laos. The JMA monitored the storm as a weak tropical depression until late on September 30, when it released its final advisory.

Late on September 27, both the Hong Kong Observatory and the Macao Meteorological and Geophysical Bureau placed Hong Kong and Macau under the Standby Signal No.1.[21][22] The Bureau then considered hoisting the Strong Wind Signal 3, but decided it was not needed for Hong Kong, while Macau hoisted it early the next day. These warnings were kept in force until later that day when all warnings were lowered.[21] On September 29 it was announced that parts of southern China would be placed under an orange warning with certain regional meteorological bureaus entering a level 3 emergency response.

On September 27, the Vietnam National Center for Hydro-Meteorological Forecasting[23] issued a public storm warning signal named "Number 9." The government instructed residents to secure their homes with fortified hard wood and sandbag roofs. Also, authorities mobilized several thousand military personnel and police to help residents evacuate from the typhoon's path. Fishing vessels were called to return to their ports.[24] This caused thousands of crops to fail.

Note:The soil can absorb between 100–150 mm with 200 mm Maximum so more than 180 mm of rain means heavy flooding. An estimated 50-80% of the rainfall in 6 hours and 65-95% of the rainfall in 9–12 hours was recorded. Pre-Post on the right side means any of the two days and is a 24-hour recorded rainfall before or after the highest 24-hour rainfall either on September 25 or September 27, 2009, September 24 or 26 for areas in Bicol Region. The soil can absorb between 40–60 mm in 6 hours without flooding, so many areas were heavily flooded and the provinces of Camarines Norte, Metro Manila, Bulacan, Batangas, Laguna, and Rizal reported widespread and very heavy flooding with moderate to low flooding occurring in the provinces of Zambales, Pampanga, Bataan, Cavite and Quezon. Ondoy's rainfall turned out to be of a flash flood type and was very unanticipated and unprepared for, which led to many deaths and extensive destruction of property.

On the afternoon of September 26, Teodoro declared an over-all state of calamity in Metro Manila and the other 25 provinces hit by the typhoon, allowing officials to utilize emergency funds for relief and rescue. Army troops, police, and civilian volunteers were deployed to rescue victims.[30] The Philippine National Red Cross and Philippine Coast Guard dispatched teams to rescue stranded and trapped people.[31] At that time, the average height of flooding was from two feet to waist high, and in some areas more than six feet.[32] Even Malacañan Palace was opened to those who were in need. The landslides and severe flooding left at least 246 people dead and 38 others missing.[8][25] Public and private roads were clogged by vehicles stuck in floodwater.[8] Thousands of motorists and more than 500 passengers were stranded at the North Luzon Expressway (NLEx). Distress calls and e-mails from thousands of Metro Manila residents and their worried relatives flooded TV and radio stations overnight as most of the power, communication, and water connections were lost.[33] Ketsana also caused flights and operations to be shut down at Ninoy Aquino International Airport for almost a day.[34]

The economic region of Metro Manila and many adjoining provinces incurred damages to both infrastructure and agriculture. As of September 28, 2009, total damages from Ketsana were estimated at $100 million.[3][4][8]Internet cafés, entertainment plazas, banks, food stores, building agencies, and stores were soaked with water and mud.[8][35] Many people were warned of leptospirosis.

Marikina City, part of Metro Manila, was the most devastated region in the Philippines: almost all of the city's area was submerged in water up to ten feet deep and tons of knee-deep mud. During the typhoon, the Marikina River broke its banks and transformed streets into rivers.[36] Marikina residential areas, particularly Provident Village, were badly affected by flooding; at least eight people were found dead.[37] Marikina itself recorded 78 deaths, the highest among Metro Manila cities.[38]

Ketsana made its landfall in Vietnam at mid-afternoon on September 29 about 37 miles (60 km) south of Da Nang, Quảng Nam Province. The first two victims were killed by falling trees and electric lines.[44] Ketsana's maximum winds were reported at 167 km/h (104 mph) with gusts as strong as 204 km/h (127 mph) as it crossed over the South China Sea and approached land.[45]

The Vietnamese government evacuated some 170,000 people as floodwater rose high to the country's six central provinces. On the evening of the same day, Ketsana was forecast to be moving toward Laos then Mukdahan in Thailand.[46][47] Heavy rains and strong winds lashed a 400 km stretch of coastline from Thừa Thiên–Huế to Quảng Ngãi, with rainfall causing massive flood surges in Huế, Bình Định, and Kon Tum provinces. Record high water levels were reported in rivers of Quảng Ngãi, Kon Tum, and Gia Lai.[48] Airports, schools, communications, and power lines in the affected area were shut down. Strong winds also destroyed parts of the North-South high voltage powerline, the backbone of Vietnam's electricity grid. The typhoon killed at least 163 people in Vietnam, 23 during the first hours after landfall; 17 people were missing and 616 injured.[24][49][50][51] Total damage of Ketsana is estimate at $785 million.[52]

The weakening typhoon struck northeastern Cambodia as one of the most severe storms ever to lash the country, with the worst damage in Kampong Thom Province in central Cambodia. Death tolls reached 43 people.[53] Also more than 66,000 families were forced from their homes by floodwaters.

There was major flooding in the southern and central provinces of Laos, and much of the country experienced heavy rain and light flooding. Water was up to knee height in the province of Saravane, and at least 26 people died. The cities of Savannakhet and Pakse were worst affected since they were directly on the pathway of the typhoon and directly on the Mekong River. In the Si Phan Don area in Champassak Province, some people took refugee on the roofs of their houses. The floods devastated rice fields and homes. Attapeu was the worst hit province, with nearly 90% of the province affected.

Ketsana moved into Thailand as a tropical depression early on September 30.[54] As the weakening cyclone moved through the country, widespread heavy rainfall and flash flooding were reported in 40 provinces.[54] The heavy rainfall also helped to fill up natural reservoirs within the country.[54] The depression partially damaged 4680 houses and destroyed 44, as well as 820,000 acres (330 000 hectares) of agricultural land.[54] Ketsana also injured one person and killed two before moving out of the country as an area of low pressure and dissipating on October 3 over the Andaman Sea.[54] Total damages were estimated at just over $20,000,000.[54] Three dams in Chai-ya-poom were damaged by the heavy rainfall, while in Pattaya nine boats were sunk waves reported to be over two metres high.[55]

The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) documented a record-high amount of rainfall in 24 hours at 455 millimetres (17.9 in). They also reported that Ketsana's rainfall was recorded from 8am PST/ 0000 (UTC) of Saturday (September 26) to 8am PST/ 0000 (UTC) of Sunday (September 27). The amount of rainfall recorded for six hours, which was 341.3 millimetres (13.44 in), was comparable to the 24-hour rainfall in 1967.[56] The damage to property was estimated to be P6 billion, including P4.1 billion in damage to infrastructure, P1.9 billion in damage to schools, and P882.525 million in damage to agriculture.[57][58]

In the Philippines, the National Disaster Coordinating Council (NDCC) headed the rescue and relief operations for the citizens affected by Ketsana's flooding. There was also a counterpart private-sector effort among companies and NGOs to provide and coordinate relief activities in various areas.

The Philippine Army deployed about 1,000 soldiers in Metro Manila and surrounding provinces to help in operations.[73] The Philippine National Red Cross and the Philippine Coast Guard also deployed teams in rubber boats to rescue people stranded in their homes.[8][74] On the Internet, citizens turned to various social networks like Twitter, Facebook, Plurk, and Multiply to share news updates and forward cries for help from people trapped in the floods. Google Maps was used to pinpoint locations of stranded people while various blogs and websites shared information on how to donate money and in-kind goods.[75] Donations arrived from all over the world and were sorely needed.

After Typhoon Ketsana and Typhoon Parma, the government of Japan has given the Philippines a P1.7-billion (3.350 billion yen) grant to improve the country's weather monitoring and information dissemination system.[76][77]

Vietnamese officials and media reported that Chinese naval forces mistreated Vietnamese fishermen who tried to take shelter from the typhoon in the disputed Paracel Islands. The Chinese Navy allegedly fired on Vietnamese fishing boats when they tried to take shelter at Tru Cau island to escape Typhoon Ketsana and after being allowed to stay on the island for several days, they were robbed and beaten by Chinese forces before leaving.[88] Vietnam and China have an agreement that fishermen from either country can ride out storms in the other's territory.

Nguyen Viet Thang, chairman of the Vietnam Fishery Association, said his organization was preparing an official protest to China over the incidents. Colonel Bui Phu Phu, vice chief of the border guard forces of the fishermen's home province of Quảng Ngãi, confirmed the accusations and said the Ministry of Foreign Affairs should send a protest to China.[89]

An official at the Chinese embassy in Hanoi said China had no comment on the accusations.

Due to the damage and deaths caused by the storm, the names Ketsana and Ondoy were later retired. The committee selected the name Champi to replace "Ketsana" on the Western Pacific basin name lists beginning in 2011. It was first used in the 2015 season. In 2012 the name selected by PAGASA to replace "Ondoy" was Odette and was first used in the 2013 season.

When PresidentBenigno Aquino III took office in June 2010, PAGASA Chief Administrator Prisco Nilo was fired and removed from his post on August 6.[90] The agency accused Nilo of having a supoosedly fool-proof forecast of Typhoon Ketsana as the typhoon struck over Metro Manila. Aquino adds lack of disaster preparedness and slow installation of Doppler weather radar and other equipment, and slow voluntary response that left the agency unmodernized.

Nilo left PAGASA after Graciano Yumul, Jr., took Nilo's vacant seat. This similar accusation also happened on the aftermath of Typhoon Basyang in July 2010. Nilo was in Australia for his new post as weather forecaster of the Australian Weather Bureau.

^Donna Miles; Lt. j.g. Theresa Donnelly (September 30, 2009). "Military Provides Rescue, Humanitarian Support in Pacific". America Forces Press Service. Retrieved October 2, 2009. Meanwhile, members of Joint Special Operations Task Force Philippines assisted the Philippine armed forces in rescuing 52 people stranded by massive flooding during Tropical Storm Ketsana earlier this week. The storm, known locally as Tropical Storm Ondoy, struck in the Manila area Sept. 27 and 28. The floods displaced hundreds of thousands of people, and the most recent reports indicate that nearly 100,000 people have been relocated, according to Philippines Disaster Management Services. Members of Navy SEAL teams and Naval Special Boat Teams 12 and 20, and U.S. medical troops attached to the Philippines task force responded, working with the island nation's military and government officials to rescue people from rooftops, deliver food and distribute medical supplies, officials reported.